For years pipe fitters have been frustrated with the problem of weld distortion in thin walled piping systems. This problem has been on the increase in recent years. Quality and cost control measures implemented by suppliers have allowed them to eliminate the extra wall thickness on pipes that was formerly characteristic of such pipe and that was expected by fitters. Thinner walls means that the ends of pipes have a tendency to be drawn toward the weld area resulting in curvature of the pipe in the longitudinal direction. That is, the heat from welding fittings and branch pipes onto the main pipe can cause it to become distorted in shape, thus necessitating rework due to improper fitup of the ends.